Oil-water mixtures resulting from industrial activities has produced serious pollution problems when discharged into the environment and even for facilities with wastewater treatment systems, the discharge of large volumes of oily waste water is an expensive and difficult treatment burden.
Machine parts or heat treated parts are often washed in parts washing tanks, and the washing solution is contaminated with manufacturing oils and heat treating quench oil and it is necessary to haul the oil-contaminated wash water away to disposal sites or for further separation treatment.
Furthermore, the separation of mixtures of oil and water include economic considerations, and work place safety and health. Contamination in the parts washing solutions and/or cutting, grinding, and metal processing operations contribute to an inefficient cleaning process which typically requires secondary cleaning and manufacturing steps to correct. The treatment and/or separation of fluids results in an added expense and time requirement to the manufacturing process.
Several types of treatment methods and systems have been developed in efforts to efficiently separate oil from water-oil mixtures. One treatment method is filtration, by which oil is entrapped by a filter and may be accomplished by conventional methods such as by barrier filters having bag and cartridge filters, or by membrane filters which are designed to remove emulsified oil from water. These types of filters tend to clog quickly, and are time consuming and expensive to replace.
Coalescers in horizontal separators is another conventional means to separate fluids. Coalescers are generally tightly packed beds of coalescing media or closely spaced plates, which aid in the separation of oil from water. Typical coalescer configurations are stacks of closely spaced plates, angled from vertical to horizontal. The plates may also be grooved or channeled, or wavy. Under the influence of gravity, oil separates from an oil/water mixture at a rate determined by Stokes law which predicts how fast an object will rise or fall through a heavier fluid based on the density and size of the object and the distance it must travel. In a packed media bed coalescer fluids are exposed to large amounts of surface area provided by the coalescing media. For instance, as an oil-water mixture passes through this media, oil droplets are temporarily held by the coalescing media where they are exposed to further contact with oil molecules in the mixture. This physical contact on the surface of the coalescer media has the effect of increasing or coalescing the size of the oil droplets in the mixture. In closely spaced plate and corrugated coalescing separators oil rises only a short distance where it is captured on the underside of the coalescing plates. The use of coalescers can improve the performance of horizontal separators; however, the coalescers are very susceptible to clogging in some separation processes.
Vertical separators generally involve discharge of an oil-water mixture into a vertical conduit, which is generally open at the bottom of a container such as a collecting tank. The mixture is discharged near either the upper end or the lower end of the tube and as the mixture flows into the tube, the oil rises and the water sinks, effecting separation of the two different fluids. The cleaner water is discharged from the bottom of the tube into the surrounding water, whereas the oil collects at the top of the tube. The oil may be collected be means of a tube and a pump, or it may be discharged by means of an overflow tube.